A backlight unit is often used as a light source for display devices such as Liquid Crystal Display (LCD) devices. Illumination level of the backlight can be adjusted low or high. For a high image quality, it is desirable to set the illumination level high (e.g., at the maximum) because setting the illumination level too low adversely affects the display quality, for example by creating visual artifacts. On the other hand, as display sizes increase and devices become more portable, power conservation concerns become increasingly important. While significant power conservation would be achieved by reducing the illumination level, for example by setting the illumination level at 50% of the maximum, the images would have visual error and noticeable artifacts (e.g., in areas of bright saturated color) with a illumination level that low.
Different methods have been developed to optimize the illumination level by balancing the image quality concerns with the power conservation goals, one of which is to dynamically adjust the illumination level as image is displayed. Today, some display panel systems utilize some form of this Dynamic Backlight Control (DBLC) to display a high-quality image at lower power usage.
Localized color dimming, whereby the backlight unit is divided into subsections that are individually controlled, works well with localized and uniform light zones. However, creating high locality and uniformity using traditional backlight designs is challenging; typically, the higher the locality, the lower the uniformity. With a traditional backlight, uniformity was achieved by situating the light sources such that the light could spread as far and wide as possible. The spreading of light, however, is not helpful when subsections of the backlight unit are controlled separately and individually because light from one subsection interferes with achieving the optimal luminance level of another subsection.
To more effectively practice localized dimming, a method and apparatus for simultaneously achieving high locality and uniformity is desired.